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Brain Power, Brain Size

When was the last time you thought about the encephalization quotient?

Yeah, same here.

It’s been awhile.

But we recently noted an article that suggests dinosaurs might have been smarter than we think. Just because they had enormous bodies, it turns out, isn’t necessarily a clear indicator of their alleged lack intelligence.

The whole concept of encephalization gets technical in hurry, as you might imagine.

First, however, we had to refresh our vocabulary.

“Cephalization” is an evolutionary trend. It means the mouth, sense organs, and nerve ganglia become concentrated at the front end of an animal.

Basically “cephalization” means there’s a head region (Wikipedia). It's associated with movement and bilateral symmetry, too. “Cephalization” led to the formation of a highly sophisticated brain in three groups of animals—arthropods, cephalopod mollusks, and vertebrates.

Side question: aren’t you glad we have a head?

Well, there are still many questions about brain evolution and brain development.

For instance, it was long believed that the brain size of anthropoid primates (both modern and extinct monkeys, humans, and alike) progressively increased over time. But in 2019 a group of scientists (American Museum of Natural History, the Chinese Academy of Sciences, and the University of California Santa Barbara) suggested that the brain enlarged repeatedly and independently over the course of anthropoid history. In fact, they found the brain may have been more complex, early on, than previously believed.

Does the encephalization quotient hold up? Maybe. Maybe not.

We humans have long gauged relative smarts based on a few things. For instance, the use of tools. Or ability to communicate. Saying someone has a “reptilian” brain means they are all instinct and lack the ability to process. Reptiles react, the theory goes. That’s all they know.

Now along comes a researcher from Vanderbilt University. Suzana Herculano-Houzel is a neuroanatomist. She used comparative anatomy and found that not all dinosaurs were created alike. She found that some dinosaurs had brain structures similar to birds. And bird brains, in case you did not know, have been found to have densely packed neurons—giving them the same relative brain capacity as mammals. (So calling someone a “birdbrain” isn’t necessarily a pejorative.)

In other words, dinosaur brains may not have been as reptilian as you might think. It’s all about what’s inside the brain, not just the size. We have long known neuron density is key. Based on Herculano-Houzel’s analysis, good old T. rex may have had 3.3 billion neurons in its cortex, which would make it as intelligent as a modern baboon.

Her work, according to this article in, indicated that the T. rex took about five years to reach maturity, lived to about 50 years old, and might have been able to use tools.

Yes, her work is drawing some criticism. But it’s clear this whole “encephalization quotient” is still being tested by scientists.

We say “good.” All theories need constant checks.

Are we humans smart enough to figure it out? We have no doubt.

Because, well, of our brain size.







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